The present invention relates to a disposable absorbent sanitary article, such as a disposable diaper for infants or for incontinent adults, comprising an absorbent pad, which is placed on a liquid impervious external backing sheet. More particularly, the invention relates to an improved sanitary article providing a very good tightness in the area of the wearer's thighs, thereby avoiding any risk of urine or faeces leakage along the wearer's legs.
Numerous arrangements have already been proposed in order to achieve such a tightness. A first one consisted in placing elastic elements in the crotch area in order to hold the article to some extent around the wearer's legs. The sanitary article comprises, in the longitudinal direction, a central part which corresponds to the crotch area and two end parts, one being a front part and the other a rear part, which correspond to the zones of the article as positioned and fixed around the wearer's waist. The elastic elements in question are fixed longitudinally along the two external edges of the backing sheet at least in the central part.
However, this first arrangement has proved insufficient insofar as the holding force which is exerted on the wearer's leg is necessarily limited and, in addition, wrinkles are created which generate leaks.
In another arrangement, it has already been proposed, in addition to the elastic elements in the crotch, to provide longitudinal flaps designed to form a barrier against transversal diffusion of faeces. Such flaps are for example described in document GB 2 161 059, in which preferably, each flap is formed by folding over a liquid-permeable protection sheet, which extends over the absorbent pad and which has the same outer shape as the liquid-permeable backing sheet. The barrier effect is achieved notably by interposing inside the folded sheet forming flap, an elastic element which is meant to pull the flap up when the sanitary article is positioned on the wearer.
Another arrangement, described in document U.S. Pat. No. 4,662,877 consists in placing on top of the absorbent pad and the impervious backing sheet, a hydrophobic covering sheet which is fixed to the backing sheet in such a way as to form a sandwich structure. The covering sheet has an opening in the crotch area and is provided with elastic elements fixed along the longitudinal edges of said opening, in a stretched condition such that they tend to pull up said longitudinal edges when the article is in position on the wearer.
Thus, there is obtained an improved barrier effect compared to document GB-2 161 059 due not only to the presence of the longitudinal flaps but also to the presence of the covering sheet on the outermost portions of the absorbent pad which provides a certain transverse protection.
Yet, despite its particularly favorable structure, the sanitary article according to document U.S. Pat. No. 4,662,877 does not provide perfect tightness, as would be expected. Indeed, even if the faeces are concentrated in the inside pouch which opens into the opening of the covering sheet, the fact nevertheless remains that when the wearer remains in the seating position, this causes a migration of liquid beyond the covering sheet and the elastic elements in the crotch area.
It is an object of the present invention to design a sanitary article which overcomes the aforesaid disadvantage. This article is, as conventionally known from document U.S. Pat. No. 4,662,877, a disposable absorbent sanitary article, such as a diaper, which comprises an absorbent pad placed between a liquid impervious external backing sheet and a hydrophobic covering sheet, both sheets having the same shape and defining, in the longitudinal direction, a central part which corresponds to the crotch area and two end parts, one being a front part and the other a rear part, which correspond to the zones of the article as positioned and fixed around the wearer's waist. The backing sheet and the covering sheet are joined together at least along their periphery and the covering sheet comprises a central opening which extends above the absorbent pad; moreover, the sanitary article comprises sets of elastic elements, disposed symmetrically with respect to the article longitudinal axis: a first set, called the crotch set, is fixed to the backing sheet and to the covering sheet along the longitudinal edges thereof, at least in the central part, and the second set is fixed to the covering sheet along the longitudinal edges of the central opening.